title: Inhibition of thymidylate synthase by hydroxyurea in rapidly proliferating P815 mastocytoma cells.
abstract: The incorporation of [14C]deoxycytidine, [3H]deoxyuridine, and [3H]thymidine, respectively into pyrimidine bases of DNA has been measured in rapidly proliferating P815 mouse mastocytoma cells in the presence of hydroxyurea. The incorporation of [14C]deoxycytidine-derived radioactivity into DNA cytosines is increased when compared to the incorporation into DNA thymines. The [3H]deoxyuridine-derived radioactivity is incorporated solely into DNA thymines and this incorporation is inhibited by hydroxyurea in a dose-dependent manner. This suggests an inhibitory effect of hydroxyurea on the thymidylate synthase which was proved in experiments in which the conversion of deoxyuridine monophosphate into deoxythymidine monophosphate catalysed by a crude enzyme preparation from P815 cells was inhibited in the presence of hydroxyurea. Enzymatic DNA methylation as measured by the conversion of incorporated [14C]deoxycytidine into 5-methylcytosines was not affected by hydroxyurea.
mesh_terms: D000818:Animals; D004273:DNA, Neoplasm / Q000096:biosynthesis*; D003841:Deoxycytidine / Q000378:metabolism; D003857:Deoxyuridine / Q000378:metabolism; D006918:Hydroxyurea / Q000494:pharmacology*; D012515:Mast-Cell Sarcoma / Q000378:metabolism*; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D051379:Mice; D013936:Thymidine / Q000378:metabolism; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*
chemical_list: D004273:DNA, Neoplasm; D003841:Deoxycytidine; D008780:Methyltransferases; D013940:Thymidylate Synthase; D013936:Thymidine; D003857:Deoxyuridine; D006918:Hydroxyurea